Opuntia robusta Wheel cactus Wheel cactus, along with all species of Opuntia cacti have been declared [Weeds of National Significance](http://weeds.ala.org.au/WoNS/opuntioidcacti/) due to their invasive nature and negative impact on native flora and fauna. Wheel cactus is drought-resistant and found throughout Australia, particularly in southern Australia, north-western and central Victoria. Established cacti can live for several decades and grow densely, hindering growth of native species and harbouring pest animals. In pastures, wheel cactus limits the grazing ability of animals as they avoid grazing due to its sharp bristles. Dense infestations of wheel cacti my also affect human activities and the barbed bristles may cause injury if coming in contact with skin. Two biocontrol agents have been released to control wheel cactus: 1. Cactoblastis *Cactoblastis cactorum* 2. Cochineal scale insect *Dactylopius opuntiae*  The combined actions of these two biocontrol ages are expected to contribute to the control of wheel cactus infestations in Australia. Of the two biocontrol agents, Dactylopius has shown the most promising results, having been observed to decrease fruit output in wheel cacti.